Groping Eels

This rune effect increases the damage from 20% to 26% weapon damage per second, while changing the graphic from zombie arms reaching out of the ground to a writing pit of eels, similar in appearance to the death animation of a Grotesque monster.

Though the damage is only 6% higher, that's per second, so it adds up to quite a bit more dealt over the full 8 seconds, especially when half a dozen or more targets are being hit by the skill.